git.zerfleddert.de Git - proxmark3-svn/blob - common/crc16.c

   1 //-----------------------------------------------------------------------------
   2 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
   3 // at your option, any later version. See the LICENSE.txt file for the text of
   4 // the license.
   5 //-----------------------------------------------------------------------------
   6 // CRC16
   7 //-----------------------------------------------------------------------------
   8
   9 #include "crc16.h"
  10
  11 unsigned short update_crc16( unsigned short crc, unsigned char c )
  12 {
  13   unsigned short i, v, tcrc = 0;
  14
  15   v = (crc ^ c) & 0xff;
  16   for (i = 0; i < 8; i++) {
  17       tcrc = ( (tcrc ^ v) & 1 ) ? ( tcrc >> 1 ) ^ 0x8408 : tcrc >> 1;
  18       v >>= 1;
  19   }
  20
  21   return ((crc >> 8) ^ tcrc)&0xffff;
  22 }